Circuits for electron discharge devices



June 1 1926.

G- D. ROBINSQN CIRCUITS FOR ELECTRON DISCHARGE DEVICES Filed Nov. 1, 192 2 Shee'ts-Sheefh 1 0 en ce q ii, W W INN,

Clttozwwi I June 1 1926. 1,587,084

G. D. ROBINSON CIRCUITS FOR ELECTRON DISCHARGE DEVICES Filed Nov. 1, 192 2 Sheets-Sheet 2 Patented June 1, 1926.

UNITED STATES 1,587,084 PATENT OFFICE. f

GORDON DUDLEY ROBINSON, OF ANNAPOLIS, mum.

cmcorrs ron ELECTRON mscn'anon nav'rcns.

Application filed November The present invention relates to methods and zmeans for controlling potentials and current flowing in circuits associated with .the electron discharge devices. In one form the invention consists in an arrangement of circuits in connection with an electrondischarge device in which the va ue of a varying current is regulated by means of a regulating current or potential whichin' itself has a varyin regulating action on the controlled on cut depending upon the frequency and decrement of the controlled ourrent or potential.

The preset invention contemplates the utilization of an arrangement of circuits associated with electron discharge devices in which a modifying or regulating efiectof a regulating current .or potential is utilized to prevent variations of the'control current or potential at certain definite frequencies while regulating to a lesser extent changes in the controlled currentorpotential at other frequencies. The modifying or reguwhereby a regulating potential is superimposed upon the actuating grid potential. It is a further object of the present invention to provide an arrangement of circuits associated with electron discharge devices whereby a regulating potential is superimposed upon the actuating grid potential'. the regulating potential having a variable value in accordance with the frequency and decrement of the current flowing in one of the associated circuits.

It is a still further object to provide an arrangement of circuits associated with electron devices in which the plate circuits are energized from an alternating current supply, and a regulating potential is superimposed upon the grid potential for the purpose of minimizing the low frequency variations in plate current. V

The present invention contemplates the use of any form of electron discharge device having one or more anodes, oneor more cathodes and one or more control members such as a grid, the electron discharge device.

preferably being of the type "in which the slope of the internal characteristic issteep 1, 1920. Serial No. 421,027.

so that relatively lar changes of plate current are produced grid potential.

In the accompanying drawings: vFlgure 1 shows diagrammatically an tr.

rangement of circuits representing a pre-' ferred form of my invent on; 7

Figure 2 a modification thereof; and Figure 3 a second modification in which the average current in each of a plurality y small changes 'of of parallel connected tubes is regulated in orderto maintain the same approximately constant in spite ofvariations of potential existing in the grid circuits of the tubes.

' Figure 4 shows a third modification in which a plurality of parallel connected tubes have their plate circuits energized froma polyp-base alternating current source, a regulatmgpotential being impressed upon the grid circuits to minimize the-low frequency variations in the average of all the plate" currents.

Referring to Figure 1, an electron discharge device' or audion 1, is'shown, having a plate 2 grid 3, and filament 4. Connected to the grid 3 1s a controlling circuit 5 adapt ed for connection to any source ofactuating potential in any well known manner such as by the coupling 6, this source of a magnitude suita'ble for the operation of the The plate or anode 2 is tube or audion. connected through a battery or. suitable source of potential 7 through a useful load 8, which may include a current indicating device. to the filament through an aperiodic impedance consisting (as shown in Figure 1) of a resistance 9 inparallel with a condenser 10. Such an impedance is differently responsive to difierent frequencies yet substantially constant over a certain useful range of frequencies. Filament battery 11 supplies energy for the'heating of the filament 4. p y

Assuming that a current is flowing from the plate 2 to the filament 4 through the tube, if by means of the grid circuit 5 'adifference of potential is established'between the grid and filament making the gridmore positive than before, a much larger current will flow from the filament 4 to the plate 2 through the external circuit. This increased current flow will in turn cause an increased drop of potential through the resistance 9 and a corresponding changein the value of the charge in the condenser 10. After the transitory state and becomes constant, the drop of potential through the resistance 9, being in "the grid filament circuit, will act in opposition to the actuating potential previously impressed upon the circuit 5 so that the change. in the anode or plate current is substantially less than would have been the case if the grid circuit 5 were not connected to the external platc'circuit at 12 so as t.o be susceptible to the drop of potential through the impedance composed of resistance 9 and condenser 10. It will therefore be seen that variations in the plate current flowing in the external circuit superimposes upon the grid a regulating potential opposite in sign to that of the actuating potential imposed upon the grid from the source 6. If, as in normal operation, a high frequency actuating potential is imposed upon the grid circuit from the source t. corresponding variations in the anode or plate current will be produced, the same flowing through the external circuit. These variations of plate current will pass through the condenser 10 readily, only the average or direct component of the plate current being compelled to pass through the resistance 9. As a. result of this, variations of plate current will be but little modified by the drop of potential through the impedance consisting of resistance 9, capacity 10, and such stray or distributed capacity as is inherent in the apparatus, while at the same time any gradual changes in the average value of plate-current will introduce a corresponding potential drop through the resistance 9, and im press upon the grid circuit a regulating potential which will tend to prevent this change. This arrangement of circuits thereby tends to keep an average constant plate current with but little effect upon any hi h frequency current flowing in the plate circuit. The circuit just described is of course adapted for reception, as well as the pro duction of high frequency oscillations.

The modification shown in Figure 2 consists of the same circuit arrangement as that described in connection with Figure 1 with the exce tion that a slightly different form of impe ance is disclosed. The impedance in this case consists of resistance or resistances 9 and inductance 13 in parallel with the condenser 10. By such construction this impedance may be made resonant to certain definite frequencies and the regulating potential impressed upon the grid circuit will have a maximum value with respect to the plate current flowing at certain desired frcquencies. The impedance may be designed to haveeither a maximum or a minimum value for any given range of frequencies. The-effectiveness of an impedance used in this circuit arrangement for regulating the anode or-platecurrent does not depend upon its absolute valuebut rather upon its'value compared to the internal impedance of the tube. lVhile not limiting nrvself to any specilic values of impedance 1) and 10, to be used by way of example it is stated that very satisfactory results were obtained where the resistance 9 was con'iposed of slightly inductive resistance unit having-alrimpedance of 1000 ohms, the condenser 10 having also an impedance value of about 1000 ohms and the internal impedance of the plate circuit was in the order of 100,000 ohms. The loop thus formed is aperiodic. i. 9., its ratio of resistance to inductance and capacity inhibits oscillations. Since the resistive impedance is substantially independent of frequency and the inductive impedance is small, the capacitive in'ipedance dctermines its action upon currents of difi'crent frequcm-ics.

In some instances it has been desirable to control the plate current by the insertion of an impedance between points 13 and Li in the plate circuit as shown in Figures 1 and 2. Such regulation demands the use of an impedance which tends to cut down the average value of plate current. By making use of circuits such as disclosed in Figures 1 and 2, however, the use of a much smaller impedance located as shown secures the desired regulation. The relationshipexistent between the values of the impedance shown in these figures and the fictitious impedance located between points 13 and 14 in the late circuit which it replaces is substantially -l-DZ, in which Z is the actual value of the impedance used and a is the amplification constant of the tube when the grid is operated with but a negligible direct component in the grid current.

Figure 3 discloses a modification in which regulating potentials are impressed upon the grid circuits of a plurality of tubes in parallel for the purpose of obtaining a definite division of load between the tubes and at the same time appreciably preventing variation in the average value of plate current. In this circuitarrangement, the filaments 20 and 21 are heated by means of alternating current, although this is of course not a neccssary requirement for the application of the present invention, the heating current being obtained from a transformer 21 having separate secondaries 22 and 23 for the tubes. Choke coils 24.- and 25 are connected across the terminals of the filaments 20 and 21 and have central taps leading therefrom through resistances 26 and 27 respectively to the plate circuit 28. 29. 30. 3 32 and Condensers 34 and 35 cooperate respectively with the impedances 26 and 27 in substantially the same manner as resistance 9 and capacity 10 in Figure 1 to impose upon the grid cireuit 34 and regulating potentials in ac cordance with the voltage dropexistent in thelexternal circuits between. filaments 20 and'21 and the int 34 in the plate circuit. I'neach of the tulies'there is therefore a tendency to hold an average definite value of anode current and there is thus a tendency 5"tdwards "a definite division .of loa 'fthe tubes. It is further obvious t at this' arrangement may be applied to any number of tubes in parallel.

The modification shown in Figure 4 dis- 1 closes'the present invention as applied to-a plurality of tubes'in parallel in which the 'plate. circuits are energized from an alternating "current source. In "this fi ure the tubes 1 havetheir filaments excite in any suitable manner as by batteries 11, the anodes fof the'tubes being connected respectively by means of circuits 36, 37 and 38 to the sec- 'ondaries 39-, 40 and 41 of low frequency transformers. The rimaries of these transformers 42, 43, an 44-are connected to a three phase alternating current source. In stead of using separate transformers a three hase transformer of any suitable type might e employed. It is also feasible to employ either two phase or single phase current to 'provide for the excitation of the platecircuit, the 'single'phase current being applied either directly to the primaries of the three transformers, 'orbeing connected thereto thru any well-known type of a phase s'plitting device so that the phasesin the secondaries of the transformers will be suitably displaced one from the other.

The other ends of the secondary winding's are connected to a common conductor at the point 45, a circuit leading from this point thru the regulating impedance 9, 10, 13 to a common point 47 to which point the 'circuit branches to the three filaments of the tubes. The grid circuits 48, 49 and 50 lead to a common point 51 which is connected to; the common plate circuit at 46, a suitable source of controlling or actuating potential being introduced in the common 45 grid circuit by the coupling 6. As here shown the coupling 6 is adapted-to energize the common portion of the grid circuits, but

the actuating potential might also be impressed separately upon the separate grid circuits at points between the common point of connection 51 and the grids. Condensers 52, 53, and 54 are placed in parallel with the secondaries of the low frequency transformers in the plate or anode circuits in order to permit the high frequency pulsations to flow in the anode circuits without interference. From the description of the circuits already given in connection with Figure 1,

it will be evident that the impedance 9, 10,

' 13 imposes upon the grid circuits of'the tubes, a regulating potential the tendency of which is to prevent variations in the plate current. In the arrangement of the, circuits shown in connection with Figure 4 the resultant variation of the plate current is pribetween of current in the plate circuits is sti marily much reducedfwhen hase cur- .rent is utilized for the excitation o f the plate 1 circu ts, the. overlapping of the phases producing a resultant' efiect which is that-of a varying direct current. By utilizing ap plicants method of applying a regulating potential to the grid circuits the varyln flow further minimized, and a tendency towards a smooth resultant of the plate current is obtained.

The particular embodiments of my invention herein disclosed are of course .susceptible to considerable variation without departing from the spirit thereof, and it is to be understood that many changes mi ht be made by those skilled in the art wit in the scope-of the invention as defined within the appended claims.

-What Ielaimis: I 1

1. The combination with an electron dis charge device having a cathode, an anode,

and a grid, of an external circuit connecting the cathode and grid and havingtherein means to impress upon said grid an actuating potential from an external source, a secondexternal circuit connecting said cathode andanode and including an indicating device and having a portion in common with said first circuit, and an aperiodic loop circuitin series with the common portion of said circuitswhereby low frequency variations in the anodecurrent are. 0 posed.

2. The combination' with an e ectron discharge device having a cathode, an anode, and a grid, of an external circuit connecting the cathode and grid and having therein means to impress upon said grid an actuating potential from an external source, a

second external circuit connecting said cathode and anode and rncludmg an 1nd1catmg device and havlng a portion 1n common wlth said first circuit, and an aperiodic loop circult COI'DPIISHlg two branches in series with v the common portion of saidcircuits, one of said branches contammg mductrve 'reactance and ohmic resistance and the other branch containing capacitive reactance, whereby sa1d loop circuit 1s more actlvely operatlve,

at a certain frequency or frequenciesthan at other frequencies whereby low frequency.

variations in theanode current are opposed.

3. The combination with an electron. discharge device having a. cathode, an anode and a grid, 'of an external circuit connecting the cathode and grid and having intercalated means to impres upon sa1d grid an actuating potential, a second external cir cuit connecting said cathode and anode and having a portion In common with said first external circuit, and an aperiodic loop in ser1es 1n the common portion of sa1d c1rcults'to oppose var1at1on of the anode current.

4. The combination with an electron dis-'.

charge device having at cathode, an anode and a grid, of an external circuit connecting the cathode and the grid and having intercalated therein means for impressing an actuating potential upon said grid, :1 second external circuit connecting said cathode and anode, said external circuits having a common portion, and means in said common portion whose impedance varies inversely 10 with the frequency to oppose low frequency variations in the anode current or potential.

5. The combination with an electron discharge device having a cathode, an anode and a grid, of an external circuit connectingthe cathode and the grid and having intercalated therein means for impressing an actuating potential upon said grid, a second external circuit connecting said cathode and anode, said external circuits having a common portion, and means controlled by the anode current in said common portion whose impedance varies inversely with the freuency to oppose low frequency variation in tie anode current.

6. The combination with an electron discharge device having a cathode, an anode \and a grid, of an external circuit connecting I he cathode and grid and having inter- ,calated therein means for impressing upon said rid anactuating potential from an externa .source, a second external circuit connecting said cathode and anode, a common portion of said circuit-s having two branches II constituting a series loop circuit, and a resistance and a capacitance respectively in said branches, said loop circuit serving to oppose variations in the anode current or potential.

7. The combination with a circuit embodying a plurality of electron discharge. devices in parallel, each having a cathode, an anode,vand a grid, of grid circuits connecting each grid to the corresponding cathode, anode circuits connecting each anode to the corresponding cathode, said anode circuits having a common conductor, a source of anode current in said conductor, a portion of each anode circuit being common to the grid circuit of the corresponding electron discharge device, and means 1n said common portion for opposing changes in the anode current of that particular device.

8. The combination with a circuit embodying a plurality of electron discharge devices in parallel, each having a cathode, an anode,

and a grid, of grid circuits connecting each grid wlth the corresponding cathode, anode circuits connecting each anode with the corresponding cathode, said anode circuits having a common conductor, a source of anode current in said common conductor, a portion of each anode circuit being common to the id circuit of the corresponding electron dlscharge device, and means in said common portion for opposing changes in the anode current of that particular device, said means being more actively operative at a certain frequency or frequencies than at other frequencies.

9. The combination with an electron discharge device having a cathode, an anode, and a grid, of an external circuit including a source of electricity to energize said cathode and connected thereto, an inductance connected in shunt across said cathode, two condensers in series connected in shunt across said cathode, aresistance connected between the midpoint of said inductance and the midpoint of said condensers, an external conductor connecting the grid with the midpoint of said condensers, and a second external conductor connecting the anode with the midpoint of said condensers.

10. The combination with a circuit employing a plurality of electron discharge devices in parallel, each having a cathode, an anode, and a grid, of an anode circuit connected to all of said anodes, a source of anode current in said anode circuit, and means for a substantially equal distribution of load be tween said devices comprising an impedance of relatively high value for a constant or slowly varying current inserted in the anode circuit of each device at a point common to the grid circuit of said device so that the voltage drop due to the anode current flowing through said impedance will be impressed upon the grid circuit of that tube.

11. In a circuit including a vacuum tube comprising a cathode, a grid and an anode, connections for energizing the said elements, a portion of said connections being common, means in said common portion for opposiiig oscillations due to electrical interaction comprising a loop circuit containing resistance and capacity, the reactance of the former being greatly in excess of that of the latter at operating frequencies.

In testimony whereof,- I aflix my signa ture.

. GORDON DUDLEY ROBINSON. 

